The proposed research effort is aimed at advancing the state-of-the-art in high-frequency (200 MHz), broadband ultrasound to provide images of malignant tumor cells and surrounding tissue. The principal types of cancer that can readily be diagnosed include oral cancer and cancer of the oropharynx; esophageal cancer and other tumors of the gastrointestinal tract (endoscopic ultrasound); skin cancer, in particular melanomas; and cancers originating within the eye (mainly intraocular melanomas). As ultrasound frequencies increase, one must adopt new transducer construction techniques to accommodate the very small spatial dimensions involved in the arrays. The microfabrication techniques proposed give rise to low-cost transducer arrays because many (100 or more) can be grown on a single silicon wafer. The baseline Phase 1 design entails the construction of two different types of lead-zirconate-titanate (PZT) transducer arrays on silicon wafers. The silicon wafer is used as one of the ultrasound backing layers. A modified sol-gel process is used to deposit a PZT thick film. In Phase I, a 32-element linear array and a 4x4 two-dimensional array will be constructed and tested to determine the feasibility of the proposed fabrication process. As part of Phase I, we will also determine the lowest transducer frequency that can take advantage of our low-cost microfabrication techniques. In one fabrication scenario, it is possible to operate the ultrasound transducer non-simultaneously at two different frequencies that have a ratio of 2 (e.g., 100 MHz and 200 MHz). In Phase 2, a full-size one-dimensional phased array with an elevation lens will be constructed as well as a two-dimensional phased array. Proper sizing of the aperture will yield lateral spatial resolutions of the order of 10-15 jim. This combined with 6 mu/m axial resolution will allow us to resolve gross cellular structure; The shrinking of the transducer array to dimensions of roughly I mm x 1 mm allows the sensor to be easily placed at the tip of an endoscope. The commercial products that will emerge from the proposed high-resolution ultrasound system include production-quality transducer assemblies, beam steering software for field programmable gate arrays, signal processing software for DSP hardware, and a comprehensive system design that can be licensed.